1. Field of the Invention
The present invention generally relates to a sheet sorting apparatus for use in association with an image forming apparatus such as, for example, a copying machine, for sorting sheets received successively from the image forming apparatus into collated sets and, more particularly, to the sheet sorting apparatus of a moving bin type including a plurality of bins or trays that move past a sheet delivery station which may be coupled with a discharge mouth of the image forming apparatus.
2. Description of the Prior Art
The sheet sorting apparatus for sorting the sheets such as copies discharged from a copying machine into collated sets generally comprises a sheet storage unit including a stack of spaced bins or trays for receiving and supporting respective collated sets of copies, and a sheet delivery unit for receiving the copies from the copying machine and then sorting them onto the bins or trays. The sheet sorting apparatus hitherto known in the art is generally available in two types, a fixed bin type and a moving bin type.
The fixed bin type includes the bins fixed in respective positions and requires the use of the sheet delivery unit that is movable up and down past a series of positions aligned with the respective positions of the bins. The moving bin type includes the bins supported for movement in spaced relation to each other relative to the sheet delivery unit that is fixed in position. The moving bin type is generally recognized advantageous in that it can be assembled in a compact size.
In view of the present invention directed to the sheet sorting apparatus of the moving bin type, reference will be made hereinafter only to the moving bin type for the discussion of the prior art.
In the moving bin type, the sorting apparatus includes at least two elongated upright cam members helically fluted to leave a plurality of helically continued threads and adapted to be driven in unison with each other. The bin-defining trays are supported by the upright cam members for movement up and down during synchronous rotation of the upright cam members. The neighboring trays are spaced a distance corresponding to the pitch between the neighboring helical threads on each of the upright cam members. This type of sorting apparatus is disclosed in, for example. U.S. Pat. No. 3,788,640, issued Jan. 29, 1974, to Stemmle, and No. 4,946,152 issued Aug. 7, 1990, to Ishikawa et al.
In order for the sheet sorting apparatus of the moving bin type to be assembled in a compact size, one desirable method is to reduce the height of the sorting apparatus itself and this may be accomplished by reducing the spacing between each neighboring trays and, hence, the spacing between one of the trays, then held in alignment with the sheet delivery unit for receiving the sheet therefrom, and the tray positioned immediately thereabove. However, undue reduction of the spacing between each neighboring trays tends to make the sheet sorting apparatus susceptible to paper jam.
The different sheet sorting apparatus has been developed which is substantially free from the problem associated with the paper jam and, yet, which is assembled in a compact size. In this different sheet sorting apparatus, arrangement has been made to provide an increased spacing between the neighboring rays only when one of them is brought into alignment with the sheet delivery unit while the reduced spacing is maintained with respect to the other trays out of alignment with the sheet delivery unit. More specifically, in this newly developed sheet sorting apparatus, each of the upright cam members referred to above is formed with a low pitch spiral camming surface region, in which the pitch between each neighboring helical threads is relatively small, and a high pitch spiral camming surface region in which the pitch between the neighboring helical threads is relatively large. The upright cam members employed in this newly developed sheet sorting apparatus are supported with their high pitch spiral camming surface regions confronting the sheet delivery unit so that when one of the trays is brought into alignment with the sheet delivery unit, the spacing between such one of the trays and the trays immediately thereabove can be increased.
Even with the newly developed sheet shorting apparatus, however, it is not possible to completely eliminate the problem associated with the paper jam. Once a paper jam occurs in the sheet sorting apparatus, a jam removal procedure must be exercised to remove one or more sheets jammed between the neighboring trays.
Accordingly, development of a sheet sorting apparatus in which the jam removal procedure can easily be performed has been longed for. Considering that the paper jam is apt to occur at a location adjacent delivery rollers in the sheet delivery unit, it has been desired to develop the sheet sorting apparatus of a type in which the paper jam occurring at portions of the trays adjacent the sheet delivery unit can easily be removed.
It is eventually pointed out that the sheet sorting apparatus has already been developed of a design wherein only a portion of each tray remote from the sheet delivery unit can be manually lifted to spread the spacing between that portion of one tray and that portion of the tray immediately above such one tray. In this new design, the jam removal is possible only when paper jam occurs in a region where the neighboring trays can be spread. However, where the paper jam occurs in a different region adjacent the sheet delivery unit, and since no means is provided to enable the opposite portion of each tray adjacent the sheet delivery unit to be lifted, the problem associated with ease to remove the paper jam is still left unsolved even in this new design.